The building and construction (B&C) segment consumes huge amounts of insulation. Because building codes require significantly more insulation in the attic as compared to elsewhere in the building envelope, residential attic ceilings are the largest insulation application. Currently, low cost fibrous insulations (loose fill fiberglass and cellulose) dominate this application. Of the foam plastics, open cell spray foam comes closest to the cost efficiency of these materials.
Most ceilings have numerous penetrations for light fixtures, utility runs, etc. Since air moves easily through fibrous insulations, the ceiling can be an area of significant energy loss due to conditioned air leakage to the outside environment. Air sealing the penetrations would solve the issue, but it's not easy to do this during the normal sequence of construction.
One approach to make the attic more airtight is to move the insulation boundary from the attic ceiling to the underside of the roof deck, using air impermeable open cell spray foam as the insulation material. The roof deck has fewer penetrations than the ceiling, and spray foam can easily be applied overhead.
This application has made the most inroads in warmer locations where attic insulation requirements are lower. In addition, construction in these markets is often slab-on-grade, which makes locating an HVAC unit in the attic sensible, thereby maximizing valuable living space below. Roof deck insulation creates a more airtight building envelope, and the HVAC unit and ductwork are now located within the conditioned/sealed space, making the operation of the unit more efficient.
This open cell spray application to the underside of the roof deck has grown over the years. However, it is not without its drawbacks. First, open cell spray foam is not a thermal (fire) barrier. Therefore, according to building code, the attic space cannot be used as living space. Second, code will not allow supply/return vents in the attic space unless a thermal barrier is in place. In the summertime the AC unit not only cools the air, it also dehumidifies. If the attic air isn't subject to dehumidification then this space can have a much higher humidity than the living area, leading to concerns about mold and rot in the roof deck.
It would, therefore, be desirable to provide improved insulated roof assemblies that address these drawbacks of open cell spray foam. Moreover, it would be desirable if such assemblies were capable of efficient prefabrication, thereby reducing onsite labor requirements and having a low total cost of construction. It would further be desirable if such assemblies provide insulation value of at least R-30, or even R-40, while embedding all insulation within the assembly and in which the insulation products used are readily available and are not difficult to manufacture. It would be further desirable have such an assembly that, as constructed, contains a weather-resistive barrier layer, an air barrier layer, a water vapor barrier layer, and thermal insulation layers. Moreover, it would be desirable to have such an assembly that is code compliant as a living and storage space, even without an interior sheathing layer. It would further be desirable to provide an assembly that bridges insulation from such a roof assembly to a floor assembly.
The present invention was made in view of the foregoing.